1. Field of the Invention
The present invention relates to power management in an electronic system such as a computer system having multiple energy-consuming electronic devices.
2. Description of the Related Art
Servers and other computer hardware are often grouped together on a rack to conserve space and place the servers and infrastructure in a central location for access by an administrator. Managing these “rack systems” can be less difficult and less expensive than separately administering a multitude of scattered servers. A variety of rack system designs are available in the market, and range in size and density. Some rack systems may be built around servers that are self-supporting in that each server has an individual chassis, on-board power supply, cooling fan, and other support devices. The self-supporting servers may be grouped in a rack or tower configuration and networked to each other and to client computers. A higher density rack system can be achieved using leaner “blade servers” with shared support modules that are connected in a multi-blade chassis. Blade servers generally achieve greater density due to having a narrower form factor and sharing support modules such as blower and power modules. Some of the more compact rack system server arrangements presently available include the SYSTEM X servers and eServer BLADECENTER available from IBM (IBM, BLADECENTER, and SYSTEM X are registered trademarks of International Business Machines Corporation, Armonk, N.Y.).
Power management is important for many aspects of operating a rack system, such as to minimize the costs of operating the servers, control the heat generated by the servers, and to optimize the performance and efficiency of the system. A feedback-based power management system may involve, for example, a motherboard having a built-in power meter circuit, ACPI, and other hardware and/or software elements. Systems may be powered by a common power supply or power distribution unit (PDU). Some of the systems include a circuit, such as a Baseboard Management Controller (BMC), that a service processor uses to monitor real-time power consumption by a server. Using this feedback, the service processor can “throttle” the processors and/or memory on the server to maintain the power consumption below a set point or “power ceiling” set by an administrator and monitored by the chassis management module.
A number of methods are known for controlling power consumption of servers individually. These methods include various methods of “power capping.” Power capping involves enforcing a power limit upon a server by selectively reducing processor performance. The server may enforce the power limit, for example, using the power meter to measure the amount of power drawn and instantaneously responding to increases in power consumption by throttling the processors and/or memory when a power threshold is reached. While power-capping techniques are useful for managing power consumption of a server individually, other system-wide parameters also need to be considered. For example, power constraints on the system as a whole need to be considered, in addition to managing power consumption to the servers individually. Furthermore, the aggregate margins between each server's power cap and its actual power consumption represents unused power availability.
Improved power-management techniques are therefore sought to address both server-level and system-level power considerations. In particular, it would be desirable to better utilize the power available to the system and to maximize throughput on the servers. It would also be desirable to provide a power management method that is responsive to the variable demands placed on the system, and which accounts for policy settings that may be imposed upon the system.